Many types of forms for bottles, vessels and the like to receive liquids and viscous products are known. Such bottles should be inexpensive, use little material and, when empty, should take up as little space as possible. They should, preferably, also be reusable for refilling of the container, bottle or vessel after use. The closure should be tight so that no liquid can escape and, preferably, should be air-tight as well.
French Patent 1 385 639 discloses a foldable bottle which, before being filled, can be compressed to have a small volume for transport. The bottom and side folds are internally directed. The folding pattern does not, however, permit substantial decrease of the volume when it is empty, and this particular bottle cannot be blow-molded.
French Utility Model Publication 2 288 445 illustrates a small bottle or ampule which is constructed in form of a longitudinal bellows, having a plurality of folds. The bottle is designed for the reception of small quantities of material which, upon compression of the bellows, can be forcefully ejected, for example through an atomizer. By pressing on the side walls in a pumping action, the content of the bottle is pressed outwardly or atomized. The invention is directed not to a flat shape of an empty container but, rather, to the elastic recovery important for the pumping action. The inwardly projecting bottom folding edges merge into the inwardly projecting side folding edges.
U.S. Pat. No. 3,395,836, Stahmer, shows an outwardly circular bottle with an inwardly extending fold so that, upon compression of the side walls, the contents can be expelled by a pumping action. The fold, similar to an accordion fold is provided to permit elastic resetting after compression rather than to reduce the volume of the bottle structure, when empty. The quantity of liquid which can be retained by this bottle is decreased by the inwardly extending wedge-shaped side walls.
Blow-molding of bottles is particularly efficient, and especially when starting from a heated plastic tube or hose. Some inherent characteristics and limitations on manufacture must be considered, however, in such a production process. The wall thickness has limits. The hot hose cannot be deformed into sharp corners, nor can the material be stretched substantially for bulges or the like due to the danger of tearing. To obtain a good folding or accordion-like or bellows-like form, thickening of material at the fold line must not occur, which is difficult to obtain in production. Problems arise at any folding process, due to compression and agglomeration of material at the fold, and stretching at points remote from the fold edge.